Field of the Invention
The invention relates to gas turbine engine composite blades and vanes and, particularly, for methods for making such blades and vanes having airfoils and dovetail roots and articles therefrom.
Description of Related Art
Bypass gas turbine engines of the turbofan type generally includes a forward fan and booster compressor, a middle core engine, and an aft low pressure power turbine. A low pressure turbine rotatably drives the fan and booster compressor via a low pressure shaft, all of which form the low pressure rotor. Composite airfoils have been developed for and used in blades and in stator vanes in such fans and booster or low pressure compressors. Such blades and vanes often have airfoils connected to dovetail roots for mounting to rotor or stator portions respectively of the engine.
Three-dimensional (3-D) braiding is a known process for forming fiber preforms by continuous intertwining of fibers. During the 3-D braiding process, a plurality of fiber carriers in a matrix array are moved simultaneously across a carrier surface. A fiber extends from each carrier member and is intertwined with fibers from other carrier members as they are simultaneously moved. The fibers are gathered above the carrier surface by suitable means. The 3-D braiding process is characterized by an absence of planes of delamination in the preform and results in a tough, crack growth resistant composite article when the preform is impregnated with resin (such as epoxy), metal or other known matrix materials. The Bluck U.S. Pat. No. 3,426,804 issued Feb. 11, 1969, and the Florentine U.S. Pat. No. 4,312,761 issued Jan. 26, 1982, illustrate machines for braiding a 3-D article preform using fiber carriers in a rectangular, row-column matrix or circular, concentric-ring matrix.
It is known to manufacture aircraft gas turbine engine blades and vanes having airfoils connected to dovetail roots from composite materials. Composite blades and vanes offer weight reduction which is highly desirable. It is desirable to have a strong blade or vane with a process for making a 3-D braided fiber preform having an airfoil and an integral dovetail root.
It is highly desirable to have a composite blade or vane with at least one integral composite airfoil and vane including a braided material outer layer. It is highly desirable to have a composite blade or vane preform with a braided material outer layer. It is highly desirable to have a method for producing a composite blade or vane preform with a braided material continuous outer layer over the airfoil and dovetail wherein the braiding process is automated and the dovetail provides an attachment feature for high-stress applications.